Now you can factor in the cost of your subs to determine how much your willing to spend or have spent to get a certain ULF perspective (category). I've input the cost of Commercial Subs, but you can also input the cost for DIY subs manually.

Calculates the cost per SI: This is an indication for the "bang for the buck" of all your subs from a ULF perspective

Calculates the cost per ULF Star: This is an indication for the "bang for the buck" for your HT from a ULF perspective (factors in room size, subs, and cost)

I've also tweaked the Star methodology: Your highest star for your lowest frequency carries forward to the other ULF frequencies. Example: If you can reach 5 stars at 10hz, you can reach 5 stars for all ULF frequencies. However if you can only reach 3 stars at 12.5hz and can reach 4.5 stars at 16hz, it will not change the 12.5z rating to 4.5 stars.

The SI Conversion charts can be found in the spreadsheet by clicking the 'plus sign' above Column L on the ULF Calculator Score tab

I thoroughly enjoy this hobby, and am always looking to expand on it. It's great to see folks excited about their subs and speak about it in these threads! There are so many great ID and commercial options available...and with DIY, the options become limitless.

With so many options, folks try to find the 'perfect' sub...they read past threads, use data-bass.com, and get the help from many AVS experienced members who have gone through this journey before. Once they select their sub(s) and set it up in their rooms, they're back to the forums to tell the world how much they enjoy them.

However, when folks start to compare their point of view with their subs system to others points of views with with other's sub systems, it's hard to understand their perspective of where they're coming from via sub models alone. They all have potentially different sub models and most certainly different listening rooms.

Objective
The purpose of this thread is to come up with a score to get us closer to understanding each sub owner's perspective from a ULF standpoint. The goal was to make it a relatively simple score that puts folks in the general ballpark based on their sub system and HT room. It will NOT be perfect. Again, this score will NOT be perfect. There are too many variables that enter into the calculation. However, the hope is that it's a 'fairly decent' assessment to give folks a better understanding of each other's HT ULF perspective.

Scoring
I've taken a shot a putting together this scoring system. Again, keep in mind that the goal was to come up with a metric that is relatively simple.

Room size in cubic feet / subwoofage in SI

The first thing to include in the metric is the size of your HT room. Your room is such a huge factor of how your sub(s) interact and perform. A dedicated sealed HT room is easy to calculate. However, if your HT is in a shared living area, you may have to factor in that entire living area. A general guideline to determine how much area to factor is:
If the opening to the next area is approximately less than half the size of the longest wall, then don't include the adjoining space. If it is larger, then include it.

The second thing to tackle with this metric is that everyone has different subs. Should we base it on overall sub displacement? Sounds reasonable, but is riddled with problems. With different designs of ported, horn, sealed, etc. and different driver capabilities (pro-audio, HT, car), pure displacement is not a fair measurement. For example: ported and horn designs will have potentially smaller drivers, but far greater output than their sealed counterparts...which kind of throws displacement out the window.

If not displacement, than how else? Using the great work of Josh Ricci and data-bass.com, I've come up with a way to normalize different model subs by comparing them to some sub standard by using the max output measured by Josh and comparing it to the standard. By using this data, we can look at subs using the same lens and make general comparisons. For example:

At 16hz, the FV15HP (in 1 port mode) has a max output of 104db. The Outlaw LFM1-EX (1 port mode) has the output of 97.5db. That is a 6.5db difference. Meaning, it would take roughly 2 LFM1-EXs to equal the output of 1 FV15HP at 16hz.

In the example above, I've essentially converted the FV15HP to 2 Outlaws at 16hz. That's how the 'conversion' works.

I mentioned sub standard above...the standard I chose to use is the SI (Stereo Integrity) HT18D2 sealed. Why? It's a popular DIY driver right now that has very good performance. It's not the best by any means, but not the worst either. Any sub would have worked that measured to 10hz, I just chose the SI as a lot of people can relate to it....and it has a very short acronym smile.gif

Now to determine how to convert a db difference (6.5 in the above example), to how many equivalent factors (multiples) is required (2 Outlaws), requires a logrithmic scale based on the below calculation:

L = 20 log (x)

Where L is the difference in db, and x is the factor (multiple). Everyone can do this in their head, right? ;) Well I've made it easier for you in the conversion chart below:

The table above are the latest listing for max output in data-bass.com. The columns show the # of SI(s) required at each ULF frequency as recorded by data-bass.com.

Also note that the gray shades above indicates that in Ricci's tests, he indicated that port noise occurred; from very apparent to very slight.

The Chart above are ESTIMATED SI conversions.

Here's the methodology I'm using for estimating (this was all derived by looking at data-bass and extrapolating from the measured results). Also, I'm estimating more optimistically in general (benefit of the doubt).

Again, this isn't perfect, but should get us pretty close.

Going from ported to sealed:

Sealed is aprox. 10db down at the ported subs tune. If the measured result is not exactly at tune, I'll subtract 1-2 db to compensate for the difference: 18hz tune, I'll use 8db down instead of 10db, since there measurement on data-bass is 20hz.

Example: The FV15HP outputs 108.1 at 20hz. The F15HP is it's sealed counterpart (using the same driver and amp), so I adjust it's 20hz output by 8db (FV15HP's tune is 18hz) to 100.1 at 20hz.

Estimating sealed max output from 20hz

Looking at data-bass, most sealed subs are down 10-12db at 12.5hz compared to 20hz. Being optimistic, I use 10db down to get to the 12.5hz

Example: Since I estimated the F15HP at 100.1 at 20hz, based on the above, it's 12.5hz output is 90.1db.

In order to determine whether or not a sealed sub can dig cleanly to 10hz, I referenced data-bass again. Looking at 20hz, the lowest output where a sealed sub has clean CEA output at 10hz is when it had 99db or higher at 20hz (LMSR12-Sealed). Generally speaking, any sealed sub that produced 99db or higher, was able to get clean output at 10hz.

To estimate 10hz output, looking at data-bass, most sealed subs are down 4-6db from 12.5hz. Being optimistic, I use 4db down from 12.5hz to get to 10hz.

Example: Since the F15HP is estimated 100.1 at 20hz (>=99db), I will estimate it's 10hz output. Subtracting 4db from it's 12.5hz estimate puts it at 86.1db at 10hz

For 16hz, I just took the midpoint between the 20hz output and the 12.5hz output.

Example: The F15HP at 20hz is 100.1, and at 12.5hz is 90.1. The 16hz output is estimated at 95.1db.

Additionally, I've added a comments in the "Notes" column for additional detail on the estimates.

I've also attached a HT ULF Calculator that will help you calculate your subwoofage in SI(s) if your sub is not listed above, but have a good guess on what the max output (ground plane) might be. I've included examples and the table above in the spreadsheet.

***Note: If your sub and/or driver isn't listed, when you post your score, please list how you estimated the output so I can add it to the list.

Comparing the two HT systems, you can see that the Rythmik system has a lower score. In this metric, lower is better. It's apparent that the Rythmik HT room generally speaking has more capable ULF at 12.5hz than the Epik room, even though the Epik room is half of the size.

When the Epik room owner speaks about not being enthusiastic about the ULF of a particular movie scene, and the Rythmik room owner loved it, this could help give us perspective on why...

Let me know what you all think! I know it isn't perfect, but if we all start calculating our HT ULF score and comparing with one another, we'll start to see if the metric is any good or not.

Please calculate and post your HT ULF score. I will update the second posts with results.

For every decrease in a 1/2 Star, the range of the score widens by 25%. No real science here for the ranges...the thought was that as you obtain more subwoofage per cubic foot of your room, the more room gain you will have (e.g. a smaller room with 2 subs will have more gain than a larger room with the same 2 subs).

Additionally, the star rating can be thought of as the amount of output you have for your size room, at the lowest frequency you care about. Some folks don't notice the very bottom octaves...could be their room, could be their furniture doesn't 'shake' at those frequencies, it could be you just can't tell a difference. Whatever the reason, it's all about your ULF perspective. You can choose what frequency you wish to measure your system at, and it will be equally weighted.

This rating doesn't care about extension, but more about clean output at the lowest frequency you care about.

My assumption is that clean output at the max levels you would listen at trump extension where you can't get to the max levels you want. In other words, a system that is high passed at 16hz but can reach clean reference output at that level, will trump a system that extends to 10hz, but has noticeable THD at 16hz to 10hz at reference; and can't get to your max levels. Said another way: clean output rules over extension that you can't cleanly get at the levels you want.

Output Estimate relative to Reference:
I've classified some of the categories from an above reference output and reference output 'lowest frequency' standpoint; meaning that if you are in the specified category, you'll generally get in-room reference output or above reference output at least at the anechoic frequency listed in your score and higher. It doesn't mean that if you're not in that category you cannot achieve that output (in room), but if you are then you likely can. Here is the reasoning for the above:

The output estimate started based some very good data that Bosso posted here. He basically stated that in his experience, the recipe for reference output was a sealed design where you would have .01 Liters of displacement per cubic foot. So for 2000 cubic feet, you would need 20 liters of displacement. 4 SI is equal to 21.2 liters of displacement. 2000cf / 4 SI = 500 ULF score....around the middle of the range. I created the categories before relating his post, so it confirmed I was in the general ballpark.

​
I am a good example that supports the above. In my 1900cf room, with just my dual FTW21s, my score is 432. The below video is during the end Hulk scene. You'll see some crazy 15hz and below content...particularly 10hz and below. This is played with a flat curve at reference. Multiple times during the video you'll notice that 5hz is the strongest frequency.

The scale on the left of the Omnimic: 130db is the very top of the chart, 120db is the first line from the top, 110 is the second, etc. etc. The horizontal axis goes from 5hz to 200hz. Fast forward to about 1:22 to see the strong 5hz content. It lasts for 20 seconds or so. At 5hz you'll see I'll hit 115db.

Like many others, I didn't start out having as capable a system that I have now.

Below is my ULF Journey:

So let's see how this plays out with the members that have contributed thus far:Member ULF Stars

Member ULF Scores

Member ULF SI Equivalents

Member Tactile Feedback FX

Let's keep things in perspective here as well. Most HT systems don't even get a star!!!! To be in the 1.5 star range, putting things in perspective, your HT experience still is very adequate and perhaps even too much for the general population!!! However, this is AVS.................

This tactile feedback from ULF can be perceived in Layers. Each layer adds to a better perception of reality or "realistic recreation of the onscreen event" (realizing this is silly and why it is in quotes). I'll explain the ULF layers in an example:

I have 4.5 Star ULF at 10hz in my 1900cf room. I sit on concrete, with 2 FV15HPs a foot behind my couch, and dual FTW21s flanking the front screen. The room is sealed with 3 concrete surfaces. I recently watched the OHF Washington Monument scene multiple times to try and get a better understanding of the different aspects of ULF perception:

I watch the scene at the main LP. ULF Layer 1 (Indirect Tactile Feedback): lots of great shaking and wobble that occurs through the ULF interacting with the couch

I watch the scene standing up, separating myself from the couch. ULF Layer 2 (Direct Tactile Feedback): I lose the effect of the couch shaking...which certainly takes away from the effect. However, my clothes are exhibiting that same shaking/wobbling, almost like a fan was on. Keep in mind, I'm standing on concrete and no other object is interacting with me. I feel the 'weightiness' of the room, and movement/wobble of my clothes.

Sitting back down again, I replay the scene appreciating all 3 Layers at once.

The point of it all, is that the combination of all of the above, adds to the overall "realism" and what I experienced "in total" sitting in my main listening position. Take one of the layers away, and you're missing the potential of the ULF effect.

Layer 1 (Indirect TF) for this scene can be recreated by high ULF that interacts to objects that are in contact with you (couch, suspended floor), and potentially be recreated by properly implemented tranducers.

Layers 2 and 3 (Direct TF) for this scene can only be recreated by high ULF.

IMO, you need them all for the full ULF experience. :)

Expanding the ULF Score: Tactile Feedback FX

The ULF score is a reflection of the overall output you have in the ULF range in your specific room, but unfortunately that doesn't tell the whole story to describing what your ULF experience is.

Why? Because everyone has different rooms with different construction (suspended floors, concrete walls, dry wall, etc.) with different furniture with different subs and with different placement of the subs. As a result, the sound waves produced by your subs will interact with those items very differently. Two people with the same ULF score could have a drastically different ULF experience because of their room's DNA so to speak.

I had originally wanted to come up with a Tactile Feedback score to augment the ULF score. The two combined would give folks a better understanding of how it "felt" to experience ULF in your room; the ULF score would give you an idea from a pressure/weight/kick in the chest standpoint, and the TF score would give you an idea from a "shaking" standpoint.

The problem with trying to come up with a Tactile Feedback score is that even that has so much variation dependent on the makeup of your room; two people with the same ULF score and suspended floors may have completely different experiences. One floor may have a resonant frequency of 6hz versus the other one having a resonant frequency of 30hz. Furniture is the same way; one type of HT seating may have a ULF resonant frequency vs the other one not having a ULF resonant frequency at all.

So instead of trying to assign a score to your room's Tactile Feedback, I believe the next best thing is to just identify Tactile Feedback enhancers (FX for short). This will at least give more details about your overall ULF experience.

Below is a list of Tactile Feedback FX that typically enhance the ULF experience:

Suspended Floor

Riser

Transducers (ULF capable)

Nearfield Sealed

Nearfield Ported

Nearfield Horn

HT seating with a ULF resonant frequency

Note that it's possible to just have 1 of these and it could potentially perform better than having all of these...it's truly dependent on the room and personal preference. However, generally speaking the more you have, the more tactile it will be.

It's always made intuitive sense that if you place subs nearfield, you will have more tactile sensation. Subs further away intuitively have less tactile sensation. In my room, ULF tactile sensation through the couch is dramatically different compared to my nearfield FV15HPs versus by 13.5ft away dual FTW21s.

BUT, if both subs produce the same SPL at the main LP, why would one sub be more tactile than the other? 100db nearfield vs 100db farfield should intuitively have the same tactile sensation, right? I've always thought it worked this way, but even though my subs are all level matched, the nearfield FV15HP's always caused more shake...so I decided to do a test:

Instead of playing a demanding ULF movie clip like WOTW or OHF, I'll play a 15hz sine wave to isolate it to a single frequency. This way it won't muddy up what frequency is really energizing the couch. I'll play the 15hz sine wave at the same SPL with the nearfield dual FV15HPs, and then the farfield dual FTW21s. After each one, I'll record the frequency response with Omnimic, and I'll also measure the tactile shake with the Vibration Meter for Androids.

As you can see, same SPL with a 15hz sine wave, but FAR more shaking from the nearfield FV15HPs.

I went a little further with this test because I wanted to see how loud I would have to go to get the same shaking with just the FTW21s.

15hz sine wave for the FTW21s. Recorded Max SPL was 117.0db.

Mean 2.4, Max 4.1

So, to get close to the tactile shaking of the nearfield FV15HPs, the farfield FTW21s had to run 20db louder!!!

The big question is: if it's not the Sound Pressure Level (SPL) that determines how much the couch shakes, then what is it?

First Theory:

The SPL is being converted into energy causing the vibration of the couch. That is why it reads the same SPL, because part of it is being absorbed. If the couch was removed, the SPL of the nearfield subs should be higher.

Test:

It completely makes sense that the SPL is getting absorbed by the couch and being converted into vibration. Thus, that is why there is more shaking nearfield. It produces the same SPL because it was already calibrated to produce that level with the couch in the way. Since the farfield subs don't have the couch in the way (at least as much as the nearfield), absorption is not as much, and less SPL is converted into the vibration in the couch.

Removing the couch away from the nearfield subs, should then increase the SPL level at the same position the mic was located as the couch is not absorbing some of the SPL. This makes complete sense and I wasn't going to test it, but because I plan on testing my ported/sealed shaking theory today...why not test it.

I moved the couch to the side of the room.

Placed a chair where the couch was, put the omnimic in the same position, and remeasured.

Still 96.6db Max SPL.......................................

So it would seem that SPL is not 'lost' in the couch and stays uniform. Theory BUSTED.

Conclusion:

Thanks to AVS Member Neutro (this thread's resident physicist) for helping me form the below:

We 'feel' sound through Sound Intensity. It is the cause for the shaking of the couch, pressure on our bodies, etc.

Sound Intensity is made up of two quantities; 1) Pressure, 2) Particle Velocity

Sound Intensity = pressure * particle velocity

Sound Intensity can also be described as Sound Power (acoustic energy) per unit Area.

To understand pressure and particle velocity better, they are analogous to Volts (pressure) and Current (particle velocity).

Pressure is measured in SPL, and Particle Velocity is measure in PVL

Sound Fields

Sound travels through various sound fields

Far Field - Pressure and Particle Velocity are always in phase. In this sound field, because they are in phase, when SPL peaks, so does PVL. Therefore, to understand tactile feedback, you just need to measure one of the quantities (SPL). When we measure SPL in the far field, we can expect that the tactile feeling will be the same regardless of the distance (e.g. 115db 25ft away will feel the same as 115db 40ft away).

Near Field - Pressure and Particle Velocity are NOT in phase (as defined by ISO 12001). This means that when PVL is at its peak, SPL is not. In fact, in the Near Field, PVL is greater than SPL in the Near Field (equation 2.25 in this paper). This is commonly referred to as "the nearfield effect".

Near Field Region - There isn't a consensus of when the near field stops and starts. From my research it's somewhere between 2 wavelengths and a 1/4 wavelength. Being conservative, we'll use a 1/4 wavelength. For ULF frequencies (20hz and down), the nearfield range starts at 14ft (20hz) to 286ft (1hz). For typical HT rooms, I would think most subs would be considered in the near field as they are 14ft away or so from the main listening positions.

***Note: Not relevant to this discussion, but this paper describes, the "Very Near Field". It is the sound field that is very close to the source where it behaves more like an incompressible fluid. This means there is very little SPL, and mostly PVL. The paper describes that this region occurs when the distance r from the moving object (speaker cone) is much smaller than both the wavelength *and* the object dimension L (eq. 2.37), which in our case would correspond to the driver diameter. Being that these ULF frequencies are much greater in length than the typical subwoofer diameter, the very near field would be the driver diameter (15in, 18in, 21in, depending on sub).

​

Results

1/4 wavelength of 15hz (test frequency) is about ~18ft. This is longest dimension of my room and thus puts all my subs in my room in the "near field".

Since all the subs are considered in the near field, SPL does not tell the whole story regarding Sound Intensity. Remember, Sound Intensity is how we 'feel' sound. In the near field, PVL is actually greater than SPL. PVL also behaves like SPL from the standpoint that the level decreases with distance (1/r^2).

Since PVL meters (Microflown) aren't readily available, I used the Vibration Meter to indirectly measure it through the couch.

The sub 13ft away measured 103db and the sub 3ft away measured 103db, but the sub 3ft away had far more tactile feeling and a greater reading on the Vibration Meter.

The reason? PVL was far greater because it was closer to the measuring source, even though SPL was the same as the sub 13ft away.

In my limited experience from the HTs where I've been able to experience both ported and sealed in the same room (albeit only 2 HTs), I've found that ported seemed to have more ULF indirect tactile feedback compared to sealed. I've tested this before in my room by swapping my nearfield subs between ported and sealed, and played the famous ULF demo clips. In every clip, the ported had far more Indirect Tactile Feedback (couch shaking). However, since they were movie clips with many frequencies occurring, it was not conclusive.

So I wanted to re-perform the test in a more controlled fashion, using a 15hz sine wave. I placed the 1 FTW21 behind the main LP ~1.5ft away from the mic, and ran the 15hz sine wave at 88db and 103db and measured the vibration using the Vibration Meter app on the android and recorded the results. I did the same using 1 FV15HP.

Here are the results:

88db 15hz sine wave test

FV15HP

Mean = 3.4

Max = 5.4

FTW21

Mean = 2.6

Max = 5.0

Observations: IMO, a difference in measurement from the Vibration Meter, but perhaps not conclusive.

103db 15hz sine wave test

FV15HP

Mean = 5.6

Max = 7.6

FTW21

Mean = 4.3

Max = 6.9

Observations: More shaking occurred with the FV15HP as the Mean values are a significant enough difference IMO. However, there also looks to be more 2nd harmonic distortion (30hz) compared to the FTW. This could be contributing to the additional shake. (I will say that even though it appears that 30hz is showing on the graph, I did not hear anything. I even played it at much higher volumes, and I didn't hear the 30hz signal.)

However...see below.

Look at 30hz and 45hz in the above plot of my Indirect Tactile Feedback using the Vibration Meter app; there is hardly any vibration going on compared to 15hz where it is the strongest. So, the 2nd and 3rd harmonic distortion (30hz and 45hz respectively) don't produce any shaking at all.

If when playing a 15hz sine wave in my room, a ported sub shakes more than sealed, and harmonic distortions (above 20hz or so) don't provide any couch shaking, what is causing the additional shaking by the ported sub?

Perhaps the ported design produces more acoustic energy than sealed? This remains unanswered...

Conclusion:

Some Background on Sound Intensity and Soundfields for context:

Quote:

We 'feel' sound through Sound Intensity. It is the cause for the shaking of the couch, pressure on our bodies, etc.

Sound Intensity is made up of two quantities; 1) Pressure, 2) Particle Velocity

Sound Intensity = pressure * particle velocity

Sound Intensity can also be described as Sound Power (acoustic energy) per unit Area.

To understand pressure and particle velocity better, they are analogous to Volts (pressure) and Current (particle velocity).

Pressure is measured in SPL, and Particle Velocity is measure in PVL

Sound Fields

Sound travels through various sound fields

Far Field - Pressure and Particle Velocity are always in phase. In this sound field, because they are in phase, when SPL peaks, so does PVL. Therefore, to understand tactile feedback, you just need to measure one of the quantities (SPL). When we measure SPL in the far field, we can expect that the tactile feeling will be the same regardless of the distance (e.g. 115db 25ft away will feel the same as 115db 40ft away).

Near Field - Pressure and Particle Velocity are NOT in phase (as defined by ISO 12001). This means that when PVL is at its peak, SPL is not. In fact, in the Near Field, PVL is greater than SPL in the Near Field (equation 2.25 in this paper). This is commonly referred to as "the nearfield effect".

Near Field Region - There isn't a consensus of when the near field stops and starts. From my research it's somewhere between 2 wavelengths and a 1/4 wavelength. Being conservative, we'll use a 1/4 wavelength. For ULF frequencies (20hz and down), the nearfield range starts at 14ft (20hz) to 286ft (1hz). For typical HT rooms, I would think most subs would be considered in the near field as they are 14ft away or so from the main listening positions.

***Note: Not relevant to this discussion, but this paper describes, the "Very Near Field". It is the sound field that is very close to the source where it behaves more like an incompressible fluid. This means there is very little SPL, and mostly PVL. The paper describes that this region occurs when the distance r from the moving object (speaker cone) is much smaller than both the wavelength *and* the object dimension L (eq. 2.37), which in our case would correspond to the driver diameter. Being that these ULF frequencies are much greater in length than the typical subwoofer diameter, the very near field would be the driver diameter (15in, 18in, 21in, depending on sub).

In the test above, I played a sealed FTW21 and a ported FV15HP level matched so they produced the same SPL the same distance away (3ft). I then measured the vibration of the couch with a FTW21, and did the same with a FV15HP. The FV15HP had greater tactile feedback on the Vibration Meter.

Since they had the same SPL in the near field, but different tactile feedback (Sound Intensity), it must be that the FV15HP produced more PVL than the FTW21. Remember, Sound Intensity = pressure (SPL) * particle velocity (PVL). If SPL stays constant, and Sound Intensity is more (via the Vibration Meter), PVL must be more.

Theory

The test above proves that a single FV15HP has more PVL than a single FTW21 in my room. However, why is that? My theory is that ported subs produce more PVL than sealed around the ported tune causing more tactile feedback in the couch, and measured by the vibration meter.

As the ported sub produces sound around tune, it uses both the driver and the port to do so. My theory is that because of this, it also produces more PVL. Since PVL is the prevalent quantity in the near field, it causes greater Sound Intensity and ultimately tactile feedback.

Since ported tunes are typically in the ULF range, perhaps the ported design is more effective at tactile feedback in that range. Additionally, if there is a difference, sub placement and room size would play part on whether or not how much of a difference you could perceive.

I wasn't able to find any other supporting evidence in the public domain on this specific theory, although I did find this:

This paper describes how a horn design was able to amplify particle velocity. Granted in this particular case, it is for *receiving* a wave and amplifying its particle velocity as opposed to *producing* a wave with more particle velocity. However, it does show that particle velocity can be amplified.

I also have a theory that larger xmax drivers also produce more PVL than their equivalent multiples of lower xmax drivers. This is just based on subjective information from these forums...no objective data.

And there lies the problem...without a PVL meter like the Microflown, it will be difficult to gather objective data.

Testing Note:

It's surprising how much more harmonic distortion there is when the mic is placed even a foot or two more close to the sub. It's also amazing how adding another sub significantly reduced the harmonic distortion.

Here is the a 101db 15hz sine wave with dual FV15HPs (1 is 1.5ft away, 1 is 3ft away):

Compare that with the 103db sine wave above, and there is quite a difference.

Move the FV15HP from 1.5ft away to 3ft away so they are both 3ft away:

This is at 96.6db for the 15hz sine wave. Compare that with the 88db, and you can see a huge difference.

Now look at the FTWs 13.5ft away:

This is at 117db Max SPL. Compare that to the 103db nearfield above, and it's a huge difference.

Indirect Tactile Feedback Measurements - My Room

Based on above, it shows that SPL as measured by an SPL measurement device does not solely determine the tactile sensation for ULF. Even though the farfield subs measured at the same SPL as the nearfield subs, the couch shaking effect was much more pronounced with the nearfield subs. I had to increase the farfield subs by 20db to get a similar shaking effect.

Below is my response with both the FTW21s and FV15HPs:

This is just the response of my FTW21s farfield:

Since nearfield subs drive the tactile feeling as compared to farfield subs, the frequency response of the nearfield subs should give a better representation of tactile feeling. In my room, the dual FV15HPs have the below nearfield response:

Based on the above, you would think I would have the most tactile feeling 25 and 50hz. I would also have good tactile feeling from 11hz to 18hz as well.

So I took the Vibration Meter and measured the vibration between the frequencies of 10hz to 80hz and plotted on a chart with the response of my nearfield FV15HPs. The main volume on the receiver as -20db for this test.

As you can see by the pink line, I get the majority of the couch shaking in my room starting at 11hz or so to about 21hz. After that, the couch shaking levels out to barely any shaking at less than 1. You can see by the blue line, that the shaking does not match the frequency response entirely, especially past 20hz where I have the strongest SPL, but the weakest couch shaking.

I have two theories why this is: 1. The resonant frequencies of my couch, 2. ULF frequencies wobble the foundation of the couch (imagine someone grabbing the base of your couch and shaking) with slower vibrations, whereas the higher LF frequencies are quicker vibrations and more directional (e.g. back massage chairs) as well as have the kick in the chest type sensations. The ladder isn't accurately measured by a phone on the based of the couch and perhaps why it drops off in the audible frequencies. It would be interesting if I could somehow measure the shaking that is happening on the cushions behind your back, as I'm sure there is lots of shaking going on in the upper bass frequencies.

Pop, is your rest of the basement open or do you have to go down the hallway to get to the open part? I know if I open my doors which are 6 feet wide it opens to another 2000 cubic foot and the theater experience is still the same. I think the room truly needs to be open where the theater is part of the room. Yours is a room with a hallway. Just count the hallway if the rest is out of site and you need to walk down the hallway to get there. I have measured with and open door and closed and the difference was negligible.

I'll let you guys be the judge. Here is my basement layout:

Does closing my curtains count as making the room sealed? If so, my score is a 95...

I wish I could demo some of these setups. My score is only 1500, but considering that I've never heard a better system (not bragging, I just don't know a lot of HT enthusiasts), I don't have a basis for comparison. Of course, if I do discover that my system is woefully inadequate, my bank account (and my wife) wouldn't be happy.

We all started at the beginning. I discovered these forums long after I had a sub so that is when the crazy starts. Seriously though, pick a goal and get there. No need for multiple sealed subs if one wants 15 hz and above. It is for the 15hz and under crowd although the Midbass is spectacular with all the sealed subs. You just can get there much cheaper.

My room isn't sealed. It opens to a hallway and the rest of the basement. I measured the open area of my basement floor plan and it came out to roughly 6,904ft^3.

Based on your listing criteria, my score is 432@10Hz.

So you can copy/paste this to your list.

popalock - 432@10hz - 16x18 SID2 powered by two FP14000 Clones

SI as the benchmark FTW...lol

Thanks! Again, not perfect, but definitely with in the ballpark to give others and idea of your ULF perspective.

You're score is definitely lower than 432...the hair trick with your wife from your HT room is proof enough of that! There's no way I could do that, and I'm at 504@10hz!

Quote:

Originally Posted by MKtheater

Pop, is your rest of the basement open or do you have to go down the hallway to get to the open part? I know if I open my doors which are 6 feet wide it opens to another 2000 cubic foot and the theater experience is still the same. I think the room truly needs to be open where the theater is part of the room. Yours is a room with a hallway. Just count the hallway if the rest is out of site and you need to walk down the hallway to get there. I have measured with and open door and closed and the difference was negligible.

^This.

Quote:

Originally Posted by MKtheater

Carp,
Pop probably should only include his hallway for space because I would think all that empty space he is showing are walls to the upstairs because those stairs are leading to empty space.

I wish I could demo some of these setups. My score is only 1500, but considering that I've never heard a better system (not bragging, I just don't know a lot of HT enthusiasts), I don't have a basis for comparison. Of course, if I do discover that my system is woefully inadequate, my bank account (and my wife) wouldn't be happy.